The current construction of the medical gas connector assemblies utilized in hospitals and the like for dispensing medical gases such as nitrous oxide, nitrogen, oxygen, etc., is such that there is a serious risk of interchanging the gas-specific portions of each connector assembly after disassembly for purposes of repair of cleaning. The gas-specific portions of the connector assemblies, for gases such as nitrogen, nitrous oxide and air, define diameter-indexed, two stage bores having a first diameter adjacent the entrance end and a smaller diameter further inward from the entrance end. The connector elements at the ends of hoses or gas using devices intended to receive the different gases are also diameter-indexed, i.e. in two steps, with a smaller diameter at the tip and a larger diameter further inwardly from the tip. In each case, the diameters of the hose connectors are complementary to the appropriate diameters of the assemblies into which they are inserted. Once inserted, the appropriate size of nut is threaded onto threads externally of the assembly, to hold the connector in place. Thus the nuts are also gas-specific. The insertion of the connector depresses a plunger located internally of the assembly, and this in turn opens a check-valve to admit gas into the connector.
A standard code has been adopted throughout North America in regard to hand-tightened assemblies for dispensing medical gases, and is known generally as the D.I.S.S. system (Diameter-Index Safey System). Simply stated, the non-interchangeable indexing is achieved by a series of increasing and decreasing diameters. Thus, the gas for which the outermost diameter is largest will also have the smallest innermost diameter. The next gas would have a slightly smaller outer diameter and a slightly larger inner diameter, and so forth. This prevents full insertion of any but the connector for the correct gas using device.
As previously stated, however, the part which defines the two-stages bore of D.I.S.S. system (as constructed by a number of manufacturers) can itself be removed by unscrewing from a rearward portion of the complete assembly, normally called the rear coupler. All of these portions, called front couplers, have identical threaded bosses with the same thread size and diameter (9/16"-18), and any one of them can be threaded into all of the rear couplers. Thus it occasionally happens that the serviceman, after disassembly for cleaning or repair, inadvertently interchanges the front couplers. In a medical situation, of course, this is highly dangerous, and could result in the administration of the wrong gas to a patient.
Described and claimed in U.S. Patent Application Ser. No. 479,532 filed on Mar. 28, 1983, now U.S. Pat. No. 4,527,587 is a valve assembly for dispensing a gas into a suitable connector, the valve assembly consisting essentially of an outer body and an inner body. The outer body has an internal passageway for the gas which opens through a front end of the outer body, and the inner body is threaded into the passageway from the front. The inner body has an internal opening which, with the passageway, defines a continuous passage. An axially movable plunger is located in the opening of the inner body, and located in the passage is a valve means which is normally closed but can be opened by rearward movement of the plunger. The plunger and the inner body have complementary, close-fitting, non-round portions, such as a hexagonal interfit, by which rotation of the plunger requires rotation of the inner body. The plunger has a means by which a suitable tool can rotate the plunger and thus also the inner body.
While the assembly described in the above-mentioned patent application functions quite well, and certainly solves a number of problems with the prior art, there is room for still further improvement in terms of safety, simplicity, lower cost, and facilitating a higher rate of gas flow.
In terms of safety, it is seen as advantageous to preclude loss of specificity through routine maintenance of the valve or valves installed into a D.I.S.S. coupler. In the structure to be described herein, the coupler is to be left affixed to its primary attachment, and the internal indexing diameters are a non-removable part of the coupler. This ensures that the internal indexing diameters are not removed during servicing.
Accordingly, it is an aspect of this invention to provide an improved valve assembly of simplified construction, lower cost and improved gas flow.
With particular reference to safety, it is an aspect of the present invention to provide a non-removable D.I.S.S. configuration in the outer body, so that during maintenance and repair of the inner body and plunger there is no risk that a non-conforming gas-using device could be connected to a partially disassembled outlet body.
It has now been found that the previous assembly described in the aforementioned patent application can be simplified by the removal of a spring used to bias the plunger into the forward position, in which position the passage through the inner body is closed and the gas is prevented from escaping. This elimination is not simply a matter of removing an element previously part of the total combination, because a realization that this removal is possible leads to a much simplified plunger and inner body construction, and in particular allows the inner body to be much smaller than previously though to be possible. Furthermore, it is possible to carry out this simplification while maintaining or even considerably improving the gas flow rate through the plunger.